It's safe to say that Who What Wear headquarters is in full-blown holiday mode these days. Visions of sugarplums, festive beauty looks, and party-outfit inspirations have been dancing in our heads--not that we're complaining, of course. Quite the contrary, dear readers, we love this time of year because it's all about parties and presents! Speaking of which, while we won't presume to know exactly what's on your wish list this year, we do know one gift you're going to get: loads of info on your favorite celebrity outfits! That's right, today we're bringing you a fresh batch of What Was She Wearing: Answers!, loaded with must-try looks from fashion favorites like Emma Watson, Sienna Miller, Nicole Richie, and more! And as per usual, we've found a handful of pitch-perfect items to help you achieve each of these desired looks, so read on for all of the need-to-know essentials!

Emma Roberts
Emma Roberts is definitely one to watch, whether you're anticipating her upcoming horror flick--Scream 4 is due to hit theaters April 2011--or just a fan of her off-duty wardrobe choices. Speaking of the latter, you were quite fond of the actress' girlish attire when she stepped out in Beverly Hills last month. The young starlet was snapped wearing a Kate Moss for Topshop Iconic Red Poppy Dress ($120, 212.966.9555) and Roger Vivier flats. Her ruffled pansy-print frock is an uber-sweet choice for the holidays, but we're also fans of A-Wear's Antique Floral Tea Dress ($45); just be sure to pair either option with opaque tights for a more winter-friendly look. To finish her adorable on-the-go ensemble, Roberts selected a Miu Miu bag, which is from a previous collection and is no longer available, and Michael Kors' Collection Oxford Sunglasses ($195, available in January). Try Hype's Jane Studded Large Shoulder Bag ($206) and Carrera's Andy Sunglasses ($98) to accessorize your floral dress a in a Roberts-like fashion.

Nicole Richie
It wasn't exactly freezing in Los Angeles last month, so we're not surprised that Nicole Richie was snapped in this leg-baring outfit just a few weeks ago. The mother/author/designer was photographed en route to a lunch in Los Angeles looking casually chic in a low-fuss, high-impact outfit. As for the details of our recent Guest Editor's outfit, she paired a loose-fit Truly Madly Deeply burnout tee with a black Isabel Marant mini skirt, Christian Louboutin Lastoto Ankle Boots ($995), and a few cool accessories, specifically a vintage Chanel bag and a beanie by The Elder Statesman. While the ensuing outfit is definitely darling, don't think you have to break the bank to recreate this stellar combo. To assemble a similar outfit, simply combine Alternative Apparel's The Versailles Slub V-Neck ($32) with Winter Kate's Tristan Skirt ($250) and Nine West's Tidel Heeled Ankle Boots ($155). Then accent your look the Richie way by adding a knit beanie, like Ann Taylor's Cashmere Beret Hat ($48), and a pair of House of Harlow 1960's Chelsea Sunglasses ($138).

Sienna Miller
If you're searching for tips on how to incorporate of-the-moment trends into your own wardrobe, look no further than fashion favorite Sienna Miller: the stunning tastemaker never fails to inspire. This time, you spotted the actress arriving at Heathrow Airport early last month sporting not one, but two of the season's must-have pieces: a chunky-knit top and cropped pants. For her jet-setting attire, Miller selected Express' Shawl-Collar Sweater ($88), which she wore over a James Perse button-up and Twenty8Twelve's Sienna Jeans ($215). You particularly liked the way Miller incorporated a subtle print by using a Temperley London scarf as a belt. For those of you looking to recreate Miller's on-trend outfit, you could always pick up her exact thick-knit sweater, but if you'd like something even more budget friendly, Forever 21's Cable Knit Cardigan ($33) in Cocoa is also a superb choice. For the rest of her ensemble, you'll want to check out Character Hero's Pleated Back-Button-Down Tunic ($54) and Paige's Skyline Ankle Peg Jeans ($189). Just don't forget to add some Miller-inspired panache to your jeans with Coach's Cheetah Ponytail Scarf ($38).

Emma Watson
Emma Watson has grown into quite the fashionable young lady over the last few years, and you've been cheering her on every step of the way. (Especially her decision to go for the perfect pixie cut!) And with the recent release of Harry Potter and the Deathly Hallows, Part One, all your attention is on the rising star and what she is wearing, of course. Most recently, you were dying to know more about the undeniably cool travel attire she was snapped wearing at London's Heathrow Airport last month. Watson incorporated a few Burberry Prorsum items into her ensemble--the Bespoke Trench Coat (which will be available in spring) and the Knight Bag ($2195)--paired with Chanel's Bow Toe Cap Flats ($498, 800.550.0005) and Ray-Ban's Original Wayfarer Sunglasses ($195). You were most drawn to Watson's edgy accents, like the jacket's black leather arms and the studded detail on her bag, so if you're looking for similar styles to work into your daily mix, be sure to check out Veda's Jones Jacket ($396) and Washington Trench ($495) with BCBGeneration's Stella Small Satchel ($128). Style them with Talbots' Suede and Patent Leather Cap-Toe Ballet Flats ($49) for an ensemble Watson is sure to approve of.

Jessica Hart
If there is one thing you love best about model Jessica Hart, it's her ability to take risks via daring outfit selections. We've seen many standout ensembles from this beauty in the past, but today's wintery look definitely tops your list. Last month Hart masterfully demonstrated her knack for mixing of-the-moment textures by pairing an Isabel Marant fur coat with The Reformation's Brandon Velvet Leggings ($95,323.203.1102). The model wore a gray button-up blouse by Don't Ask Amanda under her uber-chic jacket and finished the look with Lanvin's Grande Happy Shoulder Bag ($2445) and Rag & Bone's Wessex Boots ($495). The results are a supremely stylish uptown-meets-downtown combo that is worth replicating. To emulate this A+ outfit, we suggest starting with a luxurious coat; Guess' Faux Fur Jacket ($168) and ASOS' Long Hair Faux Fur Coat ($121) are both excellent options that are not only affordable, but will also keep you stylishly warm all season long. For the bottom half of your ensemble, you'll want to grab Madewell's Velvet Leggings ($48) and Adrien2 Brogue Ankle Boots ($135). If you're to create a head-to-toe Hart-worthy outfit, Marc by Marc Jacobs' Fantastical Tale KC Shoulder Bag ($328) is a spot-on alternative to her much pricier pick and is an equally chic selection.--Jessica Baker

Photo of Emma Roberts, courtesy of INF; photo of Nicole Richie, courtesy of X17; photo of Sienna Miller, courtesy of Bauer Griffin; photo of Emma Watson, courtesy of Burberry; photo of Jessica Hart, courtesy of Splash